A series of fronts moving into the region beginning late Sunday have the potential to be a forecasting nightmare as they will stall out and act as an unpredictable warm front/back door cold front. As discussed below in our previous post, there is a rather large spread among the models with regards to the location of the fronts and in April that usually has large temperature implications. North of the warm fronts there will be the cloudy, foggy, 50s…and south of the front there is expected to be the toasty 70s to near 80 with sunshine and some instability for the development of scattered showers and thunderstorms…especially as other boundaries approach the Mid-Atlantic. Where Philadelphia falls isn't clear cut at all. This forecast has “bust” written all over it.
Our best guess allows a cold front to move through Sunday Night into Monday Morning. This cold front comes to a stop and becomes a stalled front to our south during the daytime hours of Monday. This stalled front is expected to return as a warm front Monday Night. A cold front is then expected to swing through on Tuesday before this reverses as a warm front again for the middle of the week. Another cold front is expected to either swing through sometime between Friday and Sunday. Whether it comes through Friday or Sunday makes all the difference in temperature and sky conditions. Needless to say…this forecast will likely change this week as we get closer and closer to each day and adjustments will be required. The GFS MOS allows for 70 degree temperatures in the city to persist Monday through Thursday. Thursday and Friday look to be the cooler days to me at the moment with lots of clouds and on and off drizzle or showers. Tuesday may end up being the warmest day of the week.
With nearby fronts, shower chances were inserted into the forecast. But it likely will not rain all day and on some days this activity would be scattered at best. As we get closer and closer to each day, we will likely be able to rule out shower chances for specific time periods as it becomes clearer as to where the fronts will be placed and how much progress to the north or south they will make.